When proofs that represent the expected result of a print process are provided to a printer and the actual print process is intended to use a different color substrate, the printed product on the different color substrate will not match the customer's expected results that are represented by the supplied proofs. For example, if a proof is provided on a crème-colored paper, but the end printed product is intended to be printed on a white paper (or any other colored paper), and if the colors are not adjusted properly, the end product will not have the same color tones as the supplied proof. Pastels that are printed on the crème paper will likely look different than pastels printed on white paper if no adjustments are made. Or if a proof is provided electronically and if the colors are not adjusted properly to account for the substrate color represented by the virtual or monitor-based proof, the end product will not have the same color tones as the supplied electronic proof. Accordingly, the printer must determine how to compensate the printing process in order to account for the differences and obtain a better match with the customer's well-defined expectations.
Historically, adjustments have been made to the tone reproduction curves in the print process to get a closer match, but this usually happens by trial and error or some type of guesswork on the part of the person making the process adjustment. Errors in this parameter adjustment process are costly and inaccurate. For example, the person making the process adjustment may attempt to adjust the files in four dimensions (Cyan, Magenta, Yellow, and Black) using an ICC device link profile in order to get as close to the desired end product as possible. This creates problems because there is no way to know if the correct adjustments have been made until the image is printed on the proper substrate and the color is checked. There may be color adjustment errors due to metameric ink color differences that are not detectable until the job is printed on the press, slowing down the process and adding more expense. There is thus a need for an improved method for determining the tone reproduction change necessary to produce optimum results.